GAS-CHROMATOGRAPHY ISOTOPE RATIO MASS-SPECTROMETRY OF LEAF WAX N-ALKANES FROM PLANTS OF DIFFERING CARBON-DIOXIDE METABOLISMS

Individual n-alkanes isolated from the leaf-surface waxes of plants utilizing differing photosynthetic pathways were analysed using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), in order to obtain the ratios of C-13 to C-12 (deltaC-13). Marked differences in the average C-13-depletion of the n-alkanes relative to whole leaf tissues were observed (C3=-7.7 parts per thousand; C4=-9.9 parts per thousand; CAM=-11 parts per thousand). Additionally, all three metabolic types exhibited considerable differences of C-13-depletion between n-alkane homologues isolated from the same plant.